This invention relates to valve structures controlling flow of inlet air to a portable air powered hand held tool of a type having an outside projecting throttle valve lever controlling operation of the tool; and it is more particularly concerned with a safety air feed control valve structure or arrangement for such tools.
Portable pneumatic tools having a conventional air feed control valve structure operable by an outside projecting throttle lever are adapted to be accidentally operated under various conditions, such as when dropped, or carelessly rested with the throttle lever pressed against a bench or wall.
The general objective of the present invention is to provide an improved air feed control valve structure for such tools which avoids the possibility of being accidentally operated.
A feature of the invention lies in the association of a pair of valves controlling inlet air feed, each of which is individually manually operable by means of a separate lever, and both of which must be operated in order to activate the tool. Both valves are spring restorable. Accordingly, both control levers must be manually held operated to maintain operation of the tool. Manual release of either of the levers will inactivate the tool.
A further feature is that the usual control of air volume to the motor is maintained, in that one of the pair of valves serves the function of the usual throttle valve.
In accordance with the invention, there is provided in the handle of a pneumatically powered hand held tool, a chamber having an inlet connectible to a live air source and having an outlet connectible to an air motor or the tool, a first valve means controlling flow of source air through the inlet to the chamber, a first spring means normally biasing the first valve means closed over the inlet, a first manipulative means projecting under bias of the first spring means externally of the handle for actuating the first valve means to open condition against the bias of the first spring means; a second valve means controlling flow from the chamber through the outlet of source air admitted through the first valve means to the chamber, a second spring means normally biasing the second valve means closed over the outlet, and a second manipulative means projecting under bias of the second spring means externally of the handle for actuating the second valve means to open condition against the bias of the second spring means.